1. Field of the Invention
A method and apparatus for the fabrication or production of a longitudinally symmetrical oval concrete pipe.
2. Description of the Prior Art
Typically, round pipes used to carry or transport large volumes of water or other fluid include an enlarged circular bell end to receive the circular spigot of the next adjacent round pipe. However the terrain and water table in some areas does not permit use of round pipes with enlarged bell joints for sufficient volumes of water or other fluid to be transported. Thus oval pipes have been developed.
Commonly concrete pipes are manufactured in a vertical position employing a vibrating pipe manufacturing machine in which the inner and outer pipe forming members are removed from the pipe while the pipe is still in the machine in a vertical upright position.
Such vibration machines comprise a bottom pallet to form the bottom of the pipe as a groove or tongue, an outerform or jacket, that is positioned on the bottom pallet to form the outside of the pipe, an inner form or core positioned concentrically within the jacket to form the inside of the pipe and a top pallet positioned on top of the pipe to form a groove or a tongue.
In such vibrating machines the jacket, bottom pallet and core form a mold. A no-slump concrete mix is poured into the annular space formed between the jacket and core and compacted by vibration. After the vibrating mold is filled to a predetermined height, a top pallet is placed in pressure contact with the concrete mix in the top of the mold.
U.S. Pat. No. 3,584,356 discloses such an apparatus for forming hollow reinforced concrete at a pouring station including a bottom pallet, a pallet saddle, an outer jacket, a core mounted concentrically within and spaced from the outer jacket, means to feed concrete into the space between the core and the jacket and a top pallet holding header. Vibrators are provided on the jacket, core and header to vibrate the concrete as the mold is filled. The bottom ends of the jacket and core cooperate with sealing means incorporated in the pallet saddle to seal the bottom of the mold. More specifically, the invention includes initially lowering the jacket onto the bottom pallet, inserting and securing the top pallet to the top pallet holding header, lowering the core through the top pallet and onto the bottom pallet to complete a liquid-tight mold with the top pallet positioned ready to form the top end of the pipe. Concrete mix is poured into the mold on opposite sides of the core eliminating the need for rotating the mold while feeding the mix from a fixed point or using a rotating distributor on a non-rotating mold or some other equally complicated device. The jacket and core are vibrated simultaneously while the concrete mix is poured into the mold and additional vibration is applied to the top pallet holding header to form the top end of the pipe with the top pallet. The top pallet is released from the top pallet holding header and raised slightly. The core and jacket are stripped upwardly and the top pallet remains with the completed pipe ready to be removed from the machine.
Unfortunately alignment and fitting oval concrete pipes with such an apparatus is relatively difficult due to nonalignment of the male and female joint members formed on opposite ends of each oval concrete pipe.